1. Field of the Invention
The present invention relates to a printing apparatus for printing images by discharging ink droplets onto printing medium, in particular, to a printing apparatus of which liquid jet head unit is removably attached thereto.
2. Related Background Art
In image printing apparatus functioning as a printer, a copying machine, a facsimile or the like, or image printing apparatus used as an output unit of combined electronic equipment including a computer, a word processor and etc. as well as an output unit of a workstation, they print images on printing medium, such as printing paper and plastic sheets, in response to print signals.
Ink jet printing apparatus, for example, are constructed in such a manner that they print images on printing medium by allowing their liquid jet head unit to discharge ink in response to print signals. In such a configuration, the liquid jet head unit is commonly replaceable.
These type printing apparatus contain at least a liquid jet head unit, an ink tank, a head mounting member and a relatively moving mechanism. The head mounting member, which is referred to as carriage, is mounted removably with the liquid jet head unit.
The ink tank is connected with a pipe to the liquid jet head unit mounted on the head mounting member to supply ink to the same. The relatively moving mechanism consists, for example, of a head move mechanism for moving the head mounting member in the main scan direction and a paper conveying mechanism for moving printing medium in the sub-scan direction, and the relative movement is carried out in such a manner that the printing medium are arranged in the position opposite to the liquid jet head unit mounted on the head mounting member.
In printing apparatus having such a configuration as described above, the liquid jet head unit generally contains an ink holding portion, an input terminal and an ink discharging means, and the head mounting member generally contains a mounting member body, an output terminal, a head holding mechanism and an ink supplying member.
The ink holding portion of the liquid jet head unit contains fine liquid discharging ports (orifices) and liquid paths and temporarily holds ink supplied from an external ink tank. The input terminal of the liquid jet head unit is formed in such a manner as to be connected to the output terminal of the head mounting member, so that external print signals are input therein.
The ink discharging means of the liquid jet head unit consists, for example, of an electromechanical converting element, such as piezo element, and an electrothermal converting element, such as heating element, and allows the ink temporarily held in the ink holding portion to be discharged by the mechanical operation and heating operation corresponding to the input print signals.
The mounting member body of the head mounting member is a portion on which the liquid jet head unit is mounted, the output terminal of the same is disconnectably connected to the input terminal of the liquid jet head unit to transmit print signals, and the ink supplying member of the same supplies the ink in the ink tank to the ink holding portion of the liquid jet head unit.
The output terminal and the ink supplying member as described above are fixed to a head member body, and when mounting the liquid jet head unit on the mounting member body of the head mounting member as described above, the output terminal is connected to the input terminal by this operation, and at the same time, the ink supplying member is connected to the ink holding portion.
Although the ink supplying member may have various configurations, one example of the configurations is a hollow needle having a point in the vicinity of which is opened. In this case, the liquid jet head unit is sealed with an elastic member at least at part of its ink holding portion and has small holes previously formed therein which are closable due to their elasticity.
When the liquid jet head unit is mounted on the mounting member body of the head mounting member, the hollow needles described above are pressed into the small holes of the elastic member and allowed to pass through it by this operation. The head holding mechanism consists, for example, of a lever held in a rotatable manner and holds the liquid jet head unit mounted on the mounting member body.
In the printing apparatus described above, when the liquid jet head unit is intended to be removed from the head mounting member, first the head mounting member is released from the head holding mechanism, then the liquid jet head unit is removed from the head mounting member. The liquid jet head unit thus released from the head holding mechanism is, however, removable in any direction, accordingly, it may be removed in an inappropriate direction, so as to break the ink supplying member consisting, for example, of hollow needles.
In the configurations where hollow needles in particular, as an ink supplying member, are press fitted into small holes of the elastic member of the liquid jet head unit, the ink supplying member may easily break if the liquid jet head unit is displaced in an inappropriate direction, since the ink supplying member, which is not very strong, is held by the elastic member from the all-around direction.
In the configurations where the output terminal of the head mounting member and the input terminal of the liquid jet head unit are connected to each other by mounting the liquid jet head unit on the head mounting member, as described above, when the liquid jet head unit is intended to be removed from the head mounting member, first the output terminal and the input terminal are separated from each other, then the ink supplying member is separated from the liquid jet head unit.
This means that, an ink leak from the liquid jet head unit to the outside caused when the ink supplying member is separated from the liquid jet head unit cannot be prevented by inputting signals, since control signals cannot be externally input in the input terminal at the time of removing the ink supplying member from the liquid jet head unit.
The present invention has been made in light of the difficulties as described above. Accordingly, the object of the present invention is to provide a printing apparatus which enables removing a liquid jet head unit mounted on a head mounting member and held by a head holding mechanism easily without breaking an ink supplying member, in addition, preventing an ink leak caused when removing the liquid jet head unit mounted on a head mounting.